BASED ON THE WAY A SERIAL NUMBER IS STRUCTURED, CAN YOU PROVIDE INFO 
AS TO WHAT THE NUMBER MIGHT BE?  I FOUND AN UNIDENTIFIED NUMBER AMONG
AN ESTATE WILLED TO ME AND WONDER IF IT IS A BANK ACCOUNT FROM
SWITZERLAND OR OTHER COUNTRY.  THE NUMBER BEGINS WITH THE LETTER 'E'
AND IS FOLLOWED BY EIGHT (8) NUMERALS.

If you are not the executor, as him/her or the lawyer for the estate.

Hi, 
Here is a website that might give you some useful information:

http://www.swconsult.ch/    and here is a site linked to it about inheritance:

http://switzerland.isyours.com/e/banking/secrecy/inheriting.html

This one talks about US-Swiss matters: 
http://www.amcham.ch/switzerland/m_business_laws.htm

The trick will be to find someone who can help identify the bank,
country, or maybe that it cannot be an account number if it starts
with a letter.
Maybe the first site can help.
Do you have any indication that the deceased traveled to or
corresponded with Switzerland (probably not to a bank), or to
Luxembourg or Liechtenstein:  passport, info from another person,
anything that localize your search?
Obviously, if you decide to contact banks, start with the largest ones.
What form is the number:  handwritten, typed?  (No need to reply.)
Could it just be a telephone number?  Could the numbers be in reverse
order??
Could the E not be part of the number?  I strongly would doubt that it
would be part of a bank account number from the practicalities of
computers, but I could be wrong.

Good luck!

Does the number appear on all pages of the probate file?
It might be the case number from the probate court.

4KEITH (I'm NOT a GOOGLE Researcher)
Probate Research